Ryu's a Smash combatant now, but players familiar with the source material will have a distinct advantage over their Super Smash Bros. foes. Oh, and he's the only fighter in the series with two Final Smashes. So...he's new.
For starters, Ryu's attacks vary based on the legnth of time a button is hit. Tap for a light attack, hold for something heavier. Most of his standard attacks have light, medium and heavy versions, giving the combo-based fighter plenty to work with.
Then there are his signature moves, like the Hadouken fireball. It can be executed with the press of a button, but using the original Street Fighter inputs (quarter-circle up+A) the move will be a bit more powerful. Go half-circle+A and you'll get a Shakunetsu Hadouken.
Same goes for the Shoryuken. It can be activated with up+b, but use the original input command and, as the video says, there's a good chance you'll KO your opponent.
They have basically tweaked a whole lot of mechanics to make Ryu work in Smash while feeling familiar to Street Fighter fans. If the eShop ever works again, maybe we'll get to see how he plays.